1. Field of the Invention
The present invention relates to an inner diameter grinding wheel and a grinding apparatus using the grinding wheel to grind a cylindrical workpiece, wherein the workpiece is made of primarily, for example, glass, ceramics, silicon and like materials. The cylindrical workpiece has its inner and/or its outer peripheral surface effectively ground, and further has its edge portions effectively chamfered in the grinding operation thereof.
2. Description of the Related Art
In recent years, the need for cylindrical workpieces, for example such as silicon wafers for fabricating LSIs (i.e., large scale integrated circuits) and like integrated circuits, glass substrates for fabricating hard disks used in computers and the like is increasing. Due to this, the need for effectively grinding an outer and an inner peripheral surface of such cylindrical workpiece at a low cost is also increasing.
In the prior art as shown in FIG. 7, in general, a grinding operation of a cylindrical workpiece 12 of this kind is performed by using an outer diameter grinding wheel 45 of a conventional type which has abrasive grains bonded and fixed to its outer peripheral surface. In such grinding operation performed by using the conventional grinding wheel 45, however, it is not possible to have the grinding wheel 45 brought into contact with the workpiece 12 through a sufficiently large contact area. In other words, the conventional grinding wheel 45 is brought into substantially line-contact with the workpiece 12 during the grinding operation. Due to this, the grinding operation of the conventional grinding wheel 45 takes too much time. Further, in this grinding operation, the workpiece 12 is subjected to concentrated stress at its ground point due to the presence of a radial pressure applied thereto by the grinding wheel 45. When a diametrical feed rate of the grinding wheel 45 is increased in order to enhance the grinding operation in efficiency, the workpiece 12 such as a fragile one made of glass or like fragile material tends to break and produce chipped or broken particles of the workpiece 12. However, when such chipped or broken particles are produced during the grinding operation, the surface finish of the workpiece 12 is seriously impaired. Due to this, it is not possible to increase the diametrical feed rate of the conventional outer diameter grinding wheel 45. For the same reason, it is also not possible for the workpiece 12 to increase the rotational speed of its driven axle.
As described above, the conventional grinding apparatus for grinding the cylindrical workpiece 12 is poor in grinding efficiency, and is therefore not capable of reducing its grinding cost. These are problems inherent in the conventional grinding apparatus.
Consequently, it is an object of the present invention to solve the above problems by providing an inner diameter grinding wheel and a grinding apparatus using the inner diameter grinding wheel to precisely and effectively grind a cylindrical workpiece at a low cost, even when the workpiece is made of a fragile material such as glass and the like which tends to break and produce chipped or broken particles of the workpiece during the grinding operation.
In accordance with a first aspect of the present invention, the above object of the present invention is accomplished by providing:
An inner diameter grinding wheel provided with a doughnut-shaped main body having a bore portion, comprising a plurality of annular grinding grooves stacked together in a longitudinal direction of the bore portion of the doughnut-shaped main body to form an inner peripheral surface of the bore portion, wherein each of the annular grinding grooves assumes a trapezoidal shape in cross section, wherein the inner peripheral surface of the bore portion is coated with abrasive grains having been fixed to the inner peripheral surface, the abrasive grains being diamond or other similar hard abrasive material.
Preferably, a part of the inner peripheral surface of the bore portion of the main body is constructed of a plain peripheral surface grinding area, the plain peripheral surface grinding area being combined with the annular grinding grooves to form the inner peripheral surface of the bore portion.
Further, preferably, the annular grinding grooves differ from each other in substance and/or grain size of the abrasive grains.
In accordance with a second aspect of the present invention, the above object of the present invention is accomplished by providing:
A grinding apparatus using an inner diameter grinding wheel to grind a cylindrical workpiece, the apparatus comprising:
a grinding wheel axle support cylinder for supporting a sleeve-shaped grinding wheel axle on which the inner diameter grinding wheel is mounted, the inner diameter grinding wheel being provided with a plurality of annular grinding grooves in its inner peripheral surface, wherein the sleeve-shaped grinding wheel axle is rotatably mounted in the grinding wheel axle support cylinder to vertically pass through the grinding wheel axle support cylinder and is provided with an upper surface on which the inner diameter grinding wheel is fixedly mounted;
a rotatably driving means for rotatably driving the sleeve-shaped grinding wheel axle;
a workpiece axle support sleeve provided with a lower workpiece clamp in its upper end, to which clamp the cylindrical workpiece is attracted by the suction, wherein the workpiece axle support sleeve is freely passed through the sleeve-shaped grinding wheel axle;
the grinding wheel axle support cylinder and/or the workpiece axle support sleeve being capable of moving vertically and horizontally.
Preferably, in the grinding apparatus, the inner diameter grinding wheel is provided with a doughnut-shaped main body having a bore portion, and comprises a plurality of annular grinding grooves stacked together in a longitudinal direction of the bore portion of the doughnut-shaped main body to form an inner peripheral surface of the bore portion, wherein each of the annular grinding grooves assumes a trapezoidal shape in cross section, wherein the inner peripheral surface of the bore is coated with abrasive grains having been fixed to the inner peripheral surface, the abrasive grains being diamond or other similar hard abrasive material.
Further, preferably, in the grinding apparatus, a part of the inner peripheral surface of the bore portion of the main body is constructed of a plain peripheral surface grinding area, the plain peripheral surface grinding area being combined with the annular grinding grooves to form the inner peripheral surface of the bore portion.
Still further, preferably, in the grinding apparatus, the annular grinding grooves differ from each other in substance and/or grain size of the abrasive grains.
Preferably, the grinding apparatus further comprises an upper workpiece clamp which is coaxially arranged with the lower workpiece clamp to hold the workpiece from above, wherein the lower workpiece clamp and the upper workpiece clamp are integrally rotated.
Further, preferably, the grinding apparatus is provided with the inner peripheral surface grinding wheel, wherein the inner peripheral surface grinding wheel is rotatably supported by an inner peripheral surface grinding wheel axle support cylinder which is vertically and horizontally movable, the inner peripheral surface grinding wheel being advanced to the interior of each of the upper workpiece clamp and the lower workpiece clamp.
Preferably, the grinding apparatus further comprises a reverse rotation means for rotatably driving the workpiece axle support sleeve in a direction opposite to that of the sleeve-shaped grinding wheel axle.
In the present invention having the above construction, since the outer peripheral surface of the workpiece is grounded by utilizing the inner diameter grinding wheel, it is possible to improve the grinding operation of the workpiece in grinding efficiency without subjecting the workpiece to an excessive grinding pressure, and also possible to perform the grinding operation of the workpiece at a low cost. Further, it is also possible for the present invention to prevent the workpiece from being chipped or broken during the grinding operation, which improves the yield of finished workpieces or products. Still further, the grinding operation performed according to the present invention is remarkably excellent in accuracy and surface finish of the workpiece in comparison with the conventional grinding operation in which an outer diameter grinding wheel is used to grind the workpiece.